conventional impingement cooling systems comprise a perforated sheet metal plate disposed parallel to the surface to be cooled. Cooling air exits bores in the sheet metal plate as a series of free jets and impacts the cooling surface, and must subsequently be further transported through the gap formed by the perforated sheet metal plate and the cooling surface. The result of this is a flow transverse to the free jets. However, as the cross-flow speed increases, the deflection of the free jets increases, significantly reducing their cooling effect.
A further decrease in the cooling effect occurs when the air is heated in an uncontrollable manner from the time the cooling air enters until it exits the bores.
Applicant is aware of a gas turbine combustion chamber with impingement cooling in which the height of the cooling conduit continuously increases in the direction of the cross-flow, corresponding to the supply of cooling air, and small tubes are disposed on the perforations of the perforated sheet metal plate in such a manner that the impingement air impinges vertically upon the impingement surface, wherein the height of the small tubes increases in the cross-flow direction such that the distance of the small tubes from the impingement surface is constant over the entire length of the cooling conduit. Because of this, a constant cross-flow speed and a more uniform cooling effect are achieved. However, with this device it is not possible to completely suppress the cross-flow. But this is not desirable, because in this cooling system the cross-flow is necessary for transporting air.